Flash memory is a kind of non-volatile memory. Flash memory has advantages of fast access speed and low power consumption. Typically, flash memory may utilize memory cells with floating gates to store data. Through inject/release electrons to the floating gates, the threshold voltage distributions of the memory cells can be changed to certain data state.
However, as the density of memory devices increased and the memory cells getting more compact, effects of program disturb become more obvious. For example, when a selected memory cell in a NAND flash memory is being programmed, the threshold voltages of the nearby memory cells will be shifted due to program disturb, such that the original bias voltage settings fail to read the data correctly.